The present disclosure relates to a sheet stacking device for stacking sheets and an image forming apparatus provided with the same.
Conventionally, a technique for forming a toner image on a photoconductive drum and transferring the toner image to a sheet in a transfer unit is known as an image forming apparatus for forming an image on a sheet. The image forming apparatus includes a fixing unit and a sheet having a toner image transferred thereto is discharged after a fixing process is applied in the fixing unit.
A sheet stacking device including a sheet discharge portion is further arranged in the image forming apparatus as described above. Sheets, to which the fixing process was applied, are successively discharged and stacked on the sheet discharge portion. An actuator including a detection piece is arranged to detect the number of sheets stacked on the sheet discharge portion. The detection piece can project from and retract into an opening formed in the sheet discharge portion. The actuator is rotated by the weight of the sheets stacked on the detection piece and one end of the actuator is detected by a detector such as an optical sensor.
If a state where only one sheet is discharged on the sheet discharge portion is detected by the detection piece as described above, a small load for rotating the actuator needs to be set in correspondence with the weight of one sheet. In this case, it is difficult to detect a fully stacked state of sheets by the same detection piece. As a result, a detection piece for detecting a fully stacked state is necessary in addition to the detection piece for detecting one sheet.
The present disclosure was made in view of the above problem and aims to detect a case where a small number of sheets are stacked on a sheet discharge portion and a case where a large number of sheets are stacked by a common detection piece.